To perform a continuity check or to inspect operational characteristics of an inspection target, such as an integrated semiconductor circuit (package) or a liquid crystal panel, a probe unit that houses a plurality of contact probes, which are connection terminals, has conventionally been used to establish an electrical connection between the inspection target and a signal processing device that outputs inspection signals. As such integrated semiconductor circuits and liquid crystal panels have become highly integrated and miniaturized, having been evolved is a technology for narrowing the pitch between the contact probes so as to enable the probe unit to be used for a highly integrated and miniaturized inspection target.
Having been also disclosed is an exemplary probe unit including contact probes for electrically connecting an integrated semiconductor circuit and a circuit board, by having their ends brought into contact with an electrode of the integrated semiconductor circuit, and to an electrode of the circuit board for outputting inspection signals, respectively (see Patent Literature 1, for example).
The contact probe disclosed in Patent Literature 1 includes a first plunger that is brought into contact with the electrode of the integrated semiconductor circuit, a second plunger that is brought into contact with the electrode of the circuit board for outputting inspection signals, and a coil spring that connects the first plunger and the second plunger in an extensible and retractable manner. In the contact probe disclosed by Patent Literature 1, a first base end portion of the first plunger is housed inside a second base end portion of the second plunger having a substantially cylindrical shape, and electrical continuity is ensured by allowing the first base end portion and the second base end portion to slide with respect to each other. The first base end portion extends along the longitudinal direction of the first plunger, and the second base end portion extends along the longitudinal direction of the second plunger.